1. Field of the Invention
This invention relates to the location of leaks in pressure-assisted oil-filled electric power cables.
2. Prior Art
Oil-filled electric power cables are liable to develop leaks, particularly at cable joints. Since such cables are commonly underground, the location of such leaks presents problems. The most common method of leak location employed at present requires sectionalising the cable by repeated excavation and freezing of the cable. This is a time-consuming and expensive procedure.
In a Paper by O. Nigol in IEEE Transactions on Power Apparatus and Systems, Vol. PAS-89, No. 7, September/October 1970, there is described a hydraulic method for determining the location of oil leaks in underground cables. This method requires the presence of a sound cable alongside the leaky cable. At one end of the cable, arrangements are made to connect the leaky cable and sound cable. The oil passage in the two cables are then fed from a common reservoir or reservoirs at one end of the cable system. The oil flows in the two cables are measured. If these flows in the leaky and sound cables are Q.sub.1 and Q.sub.2 respectively, then the distance of the leak from the measuring terminal, as a fraction of the total cable length, is given by the ratio of 2Q.sub.2 to Q.sub.1 +Q.sub.2. Such a technique however requires that there should be a sound cable without any leaks and that it should be known that there are no leaks on the sound cable.